I've had this issue a few times. The five tap solution does work, but you'll need to tap the buds firmly half way along their length and count:
1 "and" 2 "and" 3 "and" 4 "and" 5 tapping each bud firmly on the number count.
If it works you should hear an ascending chime sound in both buds. If you don't hear. it has not detected the 5 taps. So, try again.
The trick is to pause between taps, ie. saying the word "and" in between
I hope this helps, sometimes its the small detail that makes the difference